Biomedical subjects

Steve K L Seah

Publications and source records attributed to Steve K L Seah.

At least 19 recordsLinked to original sources

PubMed2006

Detection of narrow angles and established angle closure in Chinese residents of Singapore: potential screening tests.

PURPOSE: To assess the performance of peripheral and central anterior chamber depth (ACD) measurements, and autorefraction, in identifying Chinese people with occludable drainage angles or established primary angle closure. DESIGN: Population-based cross-sectional analysis. METHODS: Subjects aged 40 years and older were drawn from a representative sample of Chinese Singaporean residents. Limbal chamber depth (LCD) was estimated and central ACD was measured using optical pachymetry and ultrasound. An autorefraction was taken for all subjects. Angle width and the presence of peripheral anterior synechiae were determined by gonioscopy. Receiver operating characteristic curves were generated to show the performance of these tests in detecting occludable angles. RESULTS: A total of 1090 subjects were examined. The prevalence of occludable angles was 6.5%. LCD measurement performed best in detecting occludable angles (area under the curve [AUC] 0.904, 95% confidence interval [CI] 0.870, 0.937). Optical pachymetry and ultrasound measurement of ACD performed less well (AUC 0.859 and 0.810, respectively), and autorefraction performed poorly in detecting occludable angles (AUC 0.632). LCD also gave the best performance in detecting primary angle closure (AUC 0.782, 95% CI 0.727, 0.837). CONCLUSIONS: Limbal LCD estimation outperforms other methods of measuring ACD as a screening tool for the detection of occludable drainage angles in the Chinese population of Singapore.

Adult↗

PubMed2006

Effect of trabeculectomy on lens opacities in an East Asian population.

OBJECTIVE: To examine the progression of lens opacity in Asian people after trabeculectomy and determine associated risk factors. METHODS: This was an observational case series of 243 people aged 36 to 82 years. Trabeculectomy was performed on 1 eye of each subject. Lens opacity was measured yearly using the Lens Opacification Classification System III. The main outcome measure was worsening of lens opacity defined as an increase of 2 or more Lens Opacification Classification System III units in any of the 3 lens regions, nuclear, cortical, and posterior subcapsular. Risk of progression was evaluated using logistic regression models. RESULTS: Data for 177 people were analyzed. One hundred seventeen (66%) of 177 subjects showed progression in opacity in any lens region at 3 years. Seventy-seven (66%) of 117 of those who progressed did so during the first year. Of these, 63 (82%) of 77 had lens opacity in the posterior subcapsular region. Factors associated with progression of posterior-subcapsular lens opacity at 1 year were diabetes (odds ratio, 2.4; 95% confidence interval, 1.0-5.4), use of antiglaucoma medication, dosage of topical steroid postoperatively, and being operated on by a trainee surgeon (odds ratio, 2.3; 95% confidence interval, 1.0-5.2). CONCLUSIONS: Trabeculectomy is associated with progression of lens opacity predominantly in the posterior subcapsular region. Modification of risk factors such as postoperative steroid use may delay progression.

Adult↗

PubMed2006

Peripapillary retinal nerve fiber layer thickness variations with myopia.

PURPOSE: To determine the relationship between peripapillary retinal nerve fiber layer (RNFL) thickness and myopia using optical coherence tomography (OCT). DESIGN: Prospective observational case series. METHODS: One hundred thirty-two young males with myopia (spherical equivalent [SE], -0.50 to -14.25 diopters) underwent ophthalmic examination of one randomly selected eye. Optical coherence tomography (OCT-1, version 4.1) was performed by a single operator using circular scans concentric with the optic disc with scan diameters of 3.40 mm, 4.50 mm, and 1.75 x vertical disc diameter (VDD). For each scan diameter, mean peripapillary RNFL thickness was calculated. Statistical analysis comprised repeated-measurements analysis and Pearson correlation. RESULTS: Mean peripapillary RNFL thickness did not correlate with SE for the 3.40-mm (r = -0.11, P = 0.22), 4.50-mm (r = -0.103, P = 0.24), or 1.75xVDD (r = -0.08, P = 0.36) OCT scan diameters. Neither did mean peripapillary RNFL thickness correlate with axial length for the 3.40-mm (r = -0.04, P = 0.62), 4.50-mm (r = 0.03, P=0.75), or 1.75xVDD (r = -0.02, P = 0.78) scan diameters. Mean peripapillary RNFL thicknesses for the 3.40-mm, 4.50-mm, and 1.75xVDD scans were 101.1+/-8.2 microm (95% confidence interval [CI], 99.4-102.8), 78.9+/-8.2 microm (95% CI, 77.5-80.3), and 97.5+/-10.9 microm (95% CI, 95.6-99.4), respectively. CONCLUSIONS: Mean peripapillary RNFL thickness did not vary with myopic SE or axial length for any OCT scan diameter investigated. Retinal NFL thickness measurements may be a useful parameter to assess and monitor glaucoma damage in myopic subjects.

Adult↗

PubMed2006

Changes in the optic disc after acute primary angle closure.

PURPOSE: To evaluate the changes in optic disc morphology in the first 4 months after an episode of acute primary angle closure (APAC) using stereoscopic optic disc photography and computer-assisted planimetry. DESIGN: Prospective observational case series. PARTICIPANTS: Forty-seven Asian subjects with unilateral APAC who were successfully treated with laser peripheral iridotomy (LPI). MAIN OUTCOME MEASURES: Cup-to-disc ratio (CDR) and optic cup and neuroretinal rim areas. METHODS: Stereoscopic optic disc photographs were taken 2 and 16 weeks after LPI, and the images were analyzed by computer-assisted planimetry. The overall, quadrantic, and 30 degrees sector areas of the optic disc, CDR, and neuroretinal rim area were analyzed by 2 independent masked graders, and the mean of the readings was used to calculate changes in optic disc parameters. RESULTS: The majority of the subjects were female (66%) and Chinese (90%), and the mean age was 67.6+/-11.2 years (range, 40-94). In APAC eyes from week 2 to week 16, the mean CDR increased from 0.56+/-0.05 to 0.59+/-0.03 (P<0.001), and the mean neuroretinal rim area decreased from 1.74+/-0.31 mm2 to 1.59+/-0.27 mm2 (P<0.001). Quadrantic and sector analysis showed preferential loss of neuroretinal rim area at the superotemporal and inferotemporal areas. There was no significant change in optic disc parameters in the fellow eyes over the study period. CONCLUSIONS: This study demonstrated changes in optic disc morphology from week 2 to week 16 after an episode of APAC. The pattern of optic nerve damage demonstrated in our study was comparable with that seen in primary open-angle glaucoma and experimental glaucoma models.

Acute Disease↗

PubMed2006

Long-term outcomes in fellow eyes after acute primary angle closure in the contralateral eye.

PURPOSE: To determine the long-term outcome of the contralateral eye in Asian persons with a unilateral attack of acute primary angle closure (APAC). DESIGN: Cross-sectional observational case series. PARTICIPANTS: Seventy-nine individuals who were examined from 4 to 10 years after a unilateral episode of APAC at 2 Singapore hospitals. METHODS: All subjects underwent a complete eye examination. The optic discs were graded clinically and photographically for the presence of glaucomatous optic neuropathy, and automated visual field tests were assessed for damage. All visual fields and optic nerve photographs (when available) underwent a second evaluation by a masked glaucoma specialist, who assessed whether the changes were compatible with glaucoma. MAIN OUTCOME MEASURES: Glaucomatous optic neuropathy, intraocular pressure (IOP), and visual impairment (defined as best-corrected visual acuity of worse than 6/12). RESULTS: Ninety of 138 eligible patients (65.2%) with APAC were examined, 79 with unilateral attacks. Subjects were predominantly Chinese (n = 68; 86%). There were 54 females (68%), and mean age was 68.5+/-8.9 years (standard deviation) at the time of APAC, with a mean duration of 6.3+/-1.5 years from the time of the APAC episode to the study examination. The contralateral eyes of 7 patients (8.9%) had definite or probable glaucoma, 2 of whom were felt to have glaucoma in that eye at the time of the attack. Three eyes had markedly cupped optic discs (cup-to-disc ratio > or = 0.9). Thirteen eyes (16.9%) had best-corrected vision worse than 6/12, due to cataract in almost half the cases. Only 1 eye had vision < 6/60, the cause of which was corneal decompensation. One other patient had only a central island remaining with vision of 6/12. Mean IOP of the study participants was 15.7+/-4.7 mmHg, with 6 subjects (7.6%) having undergone trabeculectomy. CONCLUSIONS: Definite or probable glaucoma was present at the time of diagnosis in 2 (2.5%) fellow eyes and developed in an additional 5 (6.5%) with a mean follow-up of 6 years. More than 80% of this cohort retained good vision in the contralateral eye, in contrast to the eye that underwent APAC. Unoperated cataract accounted for most of the visual impairment in this group.

Acute Disease↗

PubMed2006

Lens opacity, thickness, and position in subjects with acute primary angle closure.

PURPOSE: To compare lens thickness (LT), lens position (LP), relative lens position (RLP), and degree and type of lens opacity between affected and fellow eyes of subjects with acute primary angle closure (APAC) to identify any differences in lens characteristics that may be contributory to the acute episode. In addition, axial length (AL) and anterior chamber depth (ACD) measurements were evaluated. METHODS: Seventy-three study subjects with unilateral APAC were treated with sequential laser iridotomy (LI) in both eyes. Two weeks after LI, ACD, LT, and AL measurements were made in both eyes using ultrasound pachymetry. LP was defined as ACD+1/2LT and RLP as LP/AL. The Lens Opacity Classification III (LOCS III) System was used for grading lens opacity. RESULTS: The subjects were 90% Chinese and 63% female. Mean age was 61.0+/-10.9 years. Significant differences between the affected and fellow eyes were found in the ACD (2.11+/-0.35 vs 2.18+/-0.23; P=0.02) and LP (4.61+/-0.47 vs 4.75+/-0.29; P=0.02). Cortical opacity was greater in fellow eyes (0.32+/-0.72 vs 0.53+/-0.95; P=0.02). There was no difference in LT, RLP, or degree of lens opacity in the nuclear and posterior subcapsular regions. CONCLUSIONS: Compared with fellow eyes, APAC-affected eyes have shallower ACD, more anterior LP, and less cortical opacity. These differences may be contributory to APAC.

Acute Disease↗

PubMed2005

Anterior chamber depth and the risk of primary angle closure in 2 East Asian populations.

OBJECTIVE: To evaluate the risk of peripheral anterior synechiae (PAS) and glaucomatous optic neuropathy attributable to primary angle closure at varying anterior chamber depths (ACDs) in two East Asian populations. METHODS: Participants 40 years and older were from 2 population-based glaucoma surveys in Mongolia and Singapore. Central ACD was measured by optical pachymetry. Presence of PAS was determined by dynamic gonioscopy. Cases with secondary PAS were excluded. Glaucomatous optic neuropathy was diagnosed in subjects with structural and functional evidence of glaucoma. RESULTS: A total of 2032 subjects, consisting of 942 Mongolians and 1090 Chinese Singaporeans, were included in this study. A logistic model of the relationship between ACD and PAS among Singaporeans showed a consistent, incremental increase in PAS across the entire range of ACD. In deeper anterior chambers the rate of PAS exceeded that seen in Mongolians. In Mongolians, there was a clear threshold for ACD (2.4 mm) at or above which PAS were very uncommon. With ACD less than 2.4 mm, the rate of PAS rose rapidly to overtake that seen in Singaporeans. CONCLUSIONS: Shallow anterior chambers are a significant risk factor for angle closure in East Asians, although the nature of the association is specific to the individual population. There was a trend toward higher rates of glaucomatous optic neuropathy in people with the shallowest anterior chambers.

Adult↗

PubMed2005

Use of surodex in phacotrabeculectomy surgery.

PURPOSE: To evaluate the use of Surodex (Oculex Pharmaceuticals, Sunnyvale, California) a drug delivery system incorporating 60 micrograms of dexamethasone in a pellet, in phacotrabeculectomy surgery. DESIGN: Nonrandomized, prospective, interventional case series. METHODS: Phacotrabeculectomy was performed on 37 Asian subjects with primary open-angle glaucoma (POAG) using a standardized technique. All subjects received a Surodex pellet underneath the scleral flap. Results were compared with those of 31 POAG subjects who had undergone phacotrabeculectomy augmented with 50 mg/ml of intraoperative 5-fluorouracil (5-FU) during the same period. RESULTS: Mean follow-up in months was 19.7 +/- 7.9 and 22.1 +/- 6.2 for the Surodex and 5-FU groups, respectively (P = .29). There was a 20.1% decrease in intraocular pressure in the Surodex group compared with 28.5% decrease in the 5-FU group (P = .6). Postoperative complications occurred in three cases (8.1%) and six cases (19.3%), respectively (P = .04). CONCLUSIONS: Combined phacotrabeculectomy surgery augmented by intra-scleral placement of Surodex results in good control of IOP and a low incidence of complications.

Anterior Eye Segment↗

PubMed2005

Cataract progression after prophylactic laser peripheral iridotomy: potential implications for the prevention of glaucoma blindness.

PURPOSE: To evaluate changes in lens opacity in the first year after prophylactic laser peripheral iridotomy (LPI) performed in fellow eyes of subjects with acute primary angle closure (APAC). DESIGN: Prospective observational case series. PARTICIPANTS: Sixty Asian subjects with unilateral APAC. METHODS: All fellow eyes underwent prophylactic LPI within the first week of presentation, followed by 1 week of topical steroids. The degree of lens opacity was graded at the slit-lamp examination using the Lens Opacity Classification System III (LOCS III) with standard color photographs as the reference for grading of lens opacity. This was performed 2 weeks, 4 months, and 12 months after LPI. Progression in lens opacity was defined as an increase in LOCS III grade by 2 or more units in any lens region. MAIN OUTCOME MEASURES: Lens Opacity Classification Sytem III grades in nuclear, cortical, and posterior subcapsular (PSC) regions. RESULTS: Most patients were Chinese (85%) and female (63.3%), with an average age of 61.5 +/- 10.6 years. The mean baseline LOCS grades in the nuclear, cortical, and PSC regions were 3.58 +/- 0.74, 0.57 +/- 1.08, and 0.23 +/- 0.72, respectively. With 12 months of follow-up, 14 of the 60 eyes (23.3%; 95% confidence interval, 16.9-29.7%) showed significant progression in any lens region. Progression in the nuclear, cortical, and PSC regions was documented in 5%, 6.7%, and 16.7% of cases, respectively. By use of logistic regression, the following factors were not found to be significant for cataract progression in any lens region: age, race, gender, history of hypertension or diabetes, presence of peripheral anterior synechiae or angle width at baseline, and total laser energy delivered. CONCLUSIONS: In fellow eyes of APAC, prophylactic LPI is complicated by significant cataract progression, mainly in the posterior subcapsular region. These findings may have implications for the role of prophylactic LPI in the prevention of angle-closure blindness.

Acute Disease↗

PubMed2005

Iris ischaemic changes and visual outcome after acute primary angle closure.

BACKGROUND: Ischaemic changes in the iris occur frequently after an episode of acute primary angle closure (APAC). The aim of this study was to investigate the significance of such changes with regards to visual outcome. METHODS: Acute primary angle closure cases were treated with medical therapy followed by laser peripheral iridotomy after resolution of the acute episode. Subjects were examined at 1, 4, 8, 12 and 16 weeks post laser peripheral iridotomy. Eyes were examined for signs of iris ischaemic changes (IIC), defined as the presence of iris whorling or stromal atrophy. Iris photographs were also taken at weeks 1, 8 and 16. Subjects requiring glaucoma medication or filtering surgery during the follow-up period were excluded. The visual acuity and visual field (using automated white-on-white threshold perimetry) at week 16 were used in the assessment of visual outcome. RESULTS: Sixty-one subjects with APAC completed the study. The majority of subjects were female (82%) and Chinese (92%), and the mean age was 59 +/- 8.8 years. More than half the subjects (52.5%) were found to have developed IIC during the study, 65% of whom already had signs of IIC by the first week. Only 13 subjects (41%) with IIC and 6 subjects (21%) without IIC had an abnormal visual field defect at week 16 (P = 0.09). There was also no difference in visual acuity at week 16, the majority of subjects in both groups having visual acuity of 6/12 or better. CONCLUSIONS: The development of iris ischaemic changes after a single episode of APAC may not be associated with an adverse visual outcome.

Acute Disease↗

PubMed2005

Use of optical coherence tomography to assess variations in macular retinal thickness in myopia.

PURPOSE: To investigate the variation in macular retinal thickness in otherwise normal young Asian myopic subjects by using optical coherence tomography (OCT). METHODS: One hundred thirty ophthalmically normal men 19 to 24 years of age with myopia (spherical equivalent, -0.25 to -14.25 D) underwent examination of one randomly selected eye. Visual acuity, refraction, slit lamp examination, applanation tonometry, gonioscopy, A-scan ultrasound, fundus examination, visual field testing, and optic disc photography were performed. Exclusion criteria were visual acuity worse than 20/30, previous intraocular surgery, intraocular pressure >21 mm Hg, or other ocular diseases. Three horizontal transfixation and three vertical transfixation OCT scans (ver.4.1; Carl Zeiss Meditec, Dublin, CA) of 6 mm each were conducted on each eye by a single operator. Neurosensory retinal thicknesses at 100 points along each scan were measured, and the overall average, maximum, and minimum retinal thicknesses were analyzed by simple linear regression and analysis of variance. RESULTS: The average macular retinal thickness (overall) was 230.9 +/- 10.5 microm and was not significantly related to the degree of myopia. The mean maximum retinal thickness (at the parafovea) was 278.4 +/- 13.0 microm, and correlated negatively with axial length (P = 0.03). The mean minimum retinal thickness (at the foveola) was 141.1 +/- 19.1 microm, and this was positively correlated with axial length (P = 0.015) and spherical equivalent (P = 0.0002). The retina was thicker at the superior and nasal parafovea compared to the inferior or temporal parafovea. CONCLUSIONS: Average retinal thickness of the macula does not vary with myopia. However, the parafovea was thinner and the fovea thicker with myopia.

Adult↗

PubMed2005

Molecular analysis of the myocilin gene in Chinese subjects with chronic primary-angle closure glaucoma.

PURPOSE: Mutations in the myocilin (MYOC) gene have been implicated in juvenile as well as late-onset primary open-angle glaucoma (POAG). Overall, MYOC mutations account for 3% to 5% of cases of POAG worldwide, making it the most significant gene identified so far in glaucoma. Although there are some similarities in the phenotype of POAG and in particular chronic primary angle-closure glaucoma (PACG), little is known about the role of MYOC in the causation of PACG. To address this, the MYOC gene was screened in a cohort of 106 patients with chronic PACG. METHODS: Genomic DNA was extracted from leukocytes of the peripheral blood and exons 1 to 3 of the MYOC gene were PCR amplified and subjected to bidirectional sequencing and analysis. RESULTS: One hundred six patients with chronic PACG of Chinese ethnicity were studied. Sequencing of the MYOC gene in these patients revealed eight sequence variants. Of these, one was a nonsense change, three were missense changes, two were synonymous codon changes, and two were changes in noncoding sequences. These included the Arg46Stop and Thr353Ile mutations, which have been reported in individuals with POAG. However, all the sequence alterations identified have been found in normal Chinese subjects. CONCLUSIONS: The results of this study do not support a role for MYOC mutations in the pathogenesis of chronic PACG in the Chinese.

Aged↗

PubMed2004

Changes in retinal nerve fiber layer thickness after acute primary angle closure.

PURPOSE: To evaluate the changes in retinal nerve fiber layer (RNFL) thickness in the first 16 weeks after acute primary angle closure (APAC) using scanning laser polarimetry (SLP). DESIGN: Prospective, observational case series. PARTICIPANTS: Thirty-seven Asian subjects with APAC. METHODS: For all cases, APAC had resolved after treatment, and the study was conducted during the follow-up period after the acute episode. Using the GDx Nerve Fiber Analyzer (Laser Diagnostic Technologies, San Diego, CA), the RNFL was assessed in both eyes 2 weeks after APAC, and again after 16 weeks. The SLP parameters were compared between week 2 and week 16 within affected and fellow eyes. A multiple logistic regression analysis was carried out to analyze factors likely to influence RNFL outcome. MAIN OUTCOME MEASURES: Superior and inferior average RNFL thickness. RESULTS: The mean age of study subjects was 60.1+/-10.3 years (range, 46-91 years), and most subjects were female (68%) and Chinese (86%). In APAC eyes, the superior average RNFL thickness decreased from 63.8+/-13.6 microm to 61.4+/-11.2 microm (P = 0.04) and the inferior average RNFL thickness decreased from 69.5+/-14.4 microm to 66.3+/-12.6 microm (P = 0.005). There was also a decrease in inferior ratio (P = 0.008) and ellipse modulation (P = 0.02). In the fellow eyes, there was no difference found between week 2 and week 16 for any of the SLP parameters studied. Logistic regression analysis showed no significant association between developing a 10% reduction in either superior or inferior RNFL thickness with age, gender, history of ischemic risk factors, duration of symptoms during APAC, the level of presenting intraocular pressure (IOP), or the development of a rise in IOP between study visits. CONCLUSIONS: After an episode of APAC, superior and inferior average RNFL thickness was found to decrease significantly from week 2 to week 16.

Acute Disease↗

PubMed2004

Long-term outcomes in asians after acute primary angle closure.

PURPOSE: To determine the long-term outcome of Asian eyes with an acute attack of primary angle closure (APAC) and to identify risk factors at presentation associated with the development of glaucomatous optic nerve damage. DESIGN: Cross-sectional observational case series. PARTICIPANTS: Ninety individuals who were initially seen with APAC 4 to 10 years previously at 2 Singapore hospitals. METHODS: All subjects underwent a complete eye examination, including visual acuity, visual field testing, dilated eye examination, and optic nerve head photography. The optic discs were judged clinically and photographically as to whether there was glaucomatous optic neuropathy present, and visual fields were assessed for corresponding visual field loss. All visual fields and optic nerve photographs underwent a second evaluation by an experienced, but masked, glaucoma specialist, who assessed whether the changes were compatible with glaucoma. MAIN OUTCOME MEASURES: The main outcome measures were blindness (defined as best-corrected visual acuity worse than 6/60 and/or central visual field of less than 20 degrees in the attack eye) and glaucomatous optic neuropathy (GON). RESULTS: A total of 90 of 170 eligible subjects (65.2%) were examined. All subjects were Asian and were predominantly Chinese (78 subjects [86.7%]). There were 61 females (67.8%), and the age of the subjects was 62.0+/-9.0 years (mean +/- standard deviation) at the time of APAC, with a mean duration of 6.3+/-1.5 years from the time of the APAC episode to the study examination. Sixteen (17.8%) subjects were blind in the attack eye; half of the cases of blindness were caused by glaucoma. Forty-three subjects (47.8%) had GON, with 13 eyes (15.5%) having markedly cupped optic discs (cup-to-disc ratio >0.9). Thirty-eight eyes (58%) had best-corrected vision worse than 6/9, with cataract responsible for close to half the cases of poor vision. There were no identifiable risk factors related to the APAC episode that were significantly associated with the presence of GON. CONCLUSIONS: Several years after being seen with APAC, 17.8% of subjects examined were blind in the attack eye, and almost half had glaucomatous optic nerve damage. Vision was also reduced in a large number of individuals, largely from unoperated cataract. Subjects with APAC would benefit from regular follow-up to monitor for visual field decline and glaucoma development.

Acute Disease↗

PubMed2004

Acute primary angle closure: configuration of the drainage angle in the first year after laser peripheral iridotomy.

PURPOSE: To evaluate the changes in the configuration of the drainage angle in the first year after acute primary angle closure (APAC). DESIGN: Prospective observational case series. PARTICIPANTS: Forty-four Asian subjects with APAC. METHODS: Acute primary angle closure cases were treated with medical therapy followed by laser peripheral iridotomy (LPI). Static and dynamic gonioscopies were performed in APAC-affected and fellow eyes before LPI (baseline) and then at 2 weeks, 4 months, and 12 months after presentation. The angles were graded in each quadrant according to the Shaffer scheme, and the number of clock hours of peripheral anterior synechiae (PAS) was recorded. Patients who underwent intraocular surgery at any point during follow-up were excluded from the study. Intraocular pressure (IOP) and medical treatment were documented at each visit, and gonioscopic changes were correlated with the development of elevation in IOP requiring medical treatment. MAIN OUTCOME MEASURES: Average Shaffer grade and the number of clock hours of PAS. RESULTS: The majority of subjects were Chinese (84%) and female (64%), and the mean age was 60.2+/-10.7 years. At presentation, 73% of both affected and fellow eyes had very narrow angles (average Shaffer grade < or = 1), with affected eyes having more extensive PAS (P<0.001), a third of whom had > or =8 clock hours of PAS. In APAC eyes, there was a significant increase in angle width from baseline to 2 weeks after LPI (P = 0.045), but no change in angle width subsequently. Fellow eyes showed a widening of the angle between baseline and week 2 (P = 0.01) and from week 2 to month 4 (P = 0.001). There was no significant change in PAS in either affected or fellow eyes over the 12 months of follow-up. Of the 44 subjects, 19 (41.3%) subsequently developed IOP elevation during follow-up that required treatment. However, there was no difference in angle width or amount of PAS between eyes with and without a subsequent rise in IOP, and the angle configuration did not change significantly in either group over 1 year. CONCLUSION: In Asian eyes with APAC, the angle widened in the first 2 weeks after LPI, but did not change thereafter over 1 year, and the amount of PAS remained stable throughout. The results indicate the effectiveness of LPI in preventing progressive closure of the angle in the first year after APAC.

Acute Disease↗

PubMed2003

A prospective ultrasound biomicroscopy evaluation of changes in anterior segment morphology after laser iridotomy in Asian eyes.

PURPOSE: To prospectively quantify changes in anterior segment morphology after laser iridotomy using gonioscopy and ultrasound biomicroscopy (UBM). DESIGN: Prospective comparative observational case series. PARTICIPANTS: Fifty-five fellow eyes of patients presenting with acute primary angle closure (APAC). METHODS: The fellow eyes of patients presenting with APAC were examined with UBM, A-scan ultrasonography, and optical pachymetry at presentation and 2 weeks after sequential argon/neodymium yttrium-aluminum-garnet laser peripheral iridotomy (LPI). UBM images were analyzed using UBM Pro 2000 software. Baseline measurements were made both under standard lighting conditions and in darkness to look for changes in anterior segment findings. MAIN OUTCOME MEASURES: The degree of angle opening was measured using the angle-opening distance (AOD) at 250 and 500 microm from the scleral spur (AOD250 and AOD500, respectively) and angle recess area (ARA). RESULTS: Fifty-five Asian patients were examined; AOD250, AOD500, and ARA all significantly increased after sequential laser iridotomy (P < 0.002). Gonioscopic grading of the angle opening significantly increased in all 4 quadrants (P < 0.001). The Van Herick grade of limbal anterior chamber depth increased (P < 0.001), whereas the number of eyes classified as occludable decreased (73%-33%, P < 0.001). Anterior chamber depth did not change significantly (2.41 mm +/- 0.28 mm vs. 2.42 mm +/- 0.30 mm, P = 0.43) as measured with optical pachymetry. Increased illumination increased the angle-opening measures, but induced a different alteration in peripheral iris morphology. Illumination-induced changes were greater after iridotomy than before laser treatment. CONCLUSIONS: In Asian eyes at high risk of developing APAC, sequential LPI produced a significant widening of the anterior chamber angle without deepening the anterior chamber centrally. LPI produces changes in iris morphology that are different from those caused by an increase in illumination, indicating that different mechanisms account for angle opening under these 2 conditions.

Acute Disease↗

PubMed2003

Intermediate-term outcome of Baerveldt glaucoma implants in Asian eyes.

PURPOSE: To determine the intermediate-term efficacy and safety of Baerveldt glaucoma implants in Asian eyes with complicated glaucoma. DESIGN: Retrospective, nonrandomized, comparative trial. PARTICIPANTS: One hundred twenty-four Asian patients (124 eyes) with complicated glaucoma. INTERVENTION: Implantation of 54 250-mm(2) and 70 350-mm(2) Baerveldt glaucoma drainage implants at Singapore National Eye Center from 1994 through 1999. MAIN OUTCOME MEASURES: Intraocular pressure, number of glaucoma medications, and complications. RESULTS: The mean follow-up period was 33.4 +/- 14.4 months (mean +/- SD; range, 12-72 months). Intraocular pressure (IOP) was reduced from a mean preoperative IOP of 36.5 +/- 10.7 mmHg (range, 21-80 mmHg) to 15.3 +/- 6.0 mmHg (range, 1-34 mmHg), and the number of glaucoma medications decreased from 2.6 +/- 0.6 (range, 1-5) before the time of surgery to 0.5 +/- 0.9 (range, 0-4) medications at last follow-up. Overall, there were 67 eyes (54%) that were classified as complete successes, 27 eyes (22%) that were qualified successes, and 30 eyes that failed (24%). Postoperative complications occurred in 43 eyes (34.7%), and 21 eyes (17%) required further surgical intervention and revision. There was no statistically significant difference between the 250-mm(2) and 350-mm(2) type of implants in terms of success rates, final IOP, number of medications, and rates of complications. After adjusting for gender, preoperative IOP, and length of follow-up, increasing age (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.09; P = 0.02) and the number of previous operations performed before implant surgery (OR, 1.57; 95% CI, 1.07-2.31; P = 0.01) were found to be correlated positively with failure. CONCLUSIONS: In Asian eyes with complicated glaucoma, Baerveldt glaucoma implants achieve stable and satisfactory IOP reduction with low incidence of complications in the intermediate term after surgery.

Adolescent↗

PubMed2003

Refractive errors, axial ocular dimensions, and age-related cataracts: the Tanjong Pagar survey.

PURPOSE: To describe the relationship of refractive errors and axial ocular dimensions and age-related cataract. METHODS: Population-based, cross-sectional survey of ocular diseases among Chinese men and women aged 40 to 81 years (n = 1232) living in the Tanjong Pagar district in Singapore. As part of the examination, refraction and corneal curvature were determined with an autorefractor, with refraction further refined subjectively. Ocular dimensions, including axial length, anterior chamber depth, lens thickness, and vitreous chamber depth, were measured with an A-mode ultrasound device. Lens opacity was graded clinically according to the Lens Opacity Classification System (LOCS) III system. Refraction, biometry, and cataract data on right (n = 989) and left (n = 995) eyes were analyzed separately. RESULTS: In analyses controlling for age, gender, education, diabetes, and cigarette smoking, nuclear cataract was associated with myopia (-1.35 D vs. -0.11 D, P < 0.001, comparing right eyes with and without nuclear cataract), but not with any specific biometric component. Cortical cataract was associated with thinner lenses (4.67 mm vs. 4.79 mm, P = 0.001, comparing right eyes with and without cortical cataract), but not with refraction and other biometric components. Posterior subcapsular cataract was associated with myopia (-1.80 D vs. -0.39 D, P < 0.001, comparing right eyes with and without posterior subcapsular cataract), deeper anterior chamber (3.00 mm vs. 2.89 mm, P = 0.02), thinner lens (4.62 mm vs. 4.77 mm, P = 0.001), and longer vitreous chamber (15.78 mm vs. 15.57 mm, P = 0.09), but not with overall axial length and corneal curvature. Adjustment for vitreous chamber depth attenuated the association between posterior subcapsular cataract and myopia by 65.5%, but did not substantially change the association between nuclear cataract and myopia. CONCLUSIONS: These population-based data support the associations between nuclear and posterior subcapsular cataracts and myopia reported in previous studies. Posterior subcapsular cataract is also associated with deeper anterior chamber, thinner lens, and longer vitreous chamber, with vitreous chamber depth explaining most of the association between posterior subcapsular cataract and myopia.

Adult↗